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PHYSICS REVISION Full topics Question1. a. Write down the gravitational unit of force. How is it related to Newton? b. A water pump raises 50 litres of water through a height of 25 m in 5 s. Calculate the power which the pump supplies. [Take g = 10 Nkg 1 and density of water = 1000kgm 3] [Ans: 2500W] c. Name the three classes of levers and distinguish between them. Give two examples of each. d. A man weighs 600 N on the earth. What would be his approximate weight on the moon? What is the reason for your answer? [Ans: 100N; weight on moon is one sixth the weight on earth] e. Give an example when work done by the force of gravity acting on a body is zero even though the body gets displaced from its initial position. Question2. a. If the power of a motor is 40 kW, at what speed can it raise a load of 20,000 N? [Ans: 2m/s] b. A ray of light, after refraction through a concave lens emerges parallel to the principal axis. Draw a ray diagram to show the incident ray and its corresponding emergent ray. c. Draw a diagram to show how a converging lens can form a real and enlarged image of an object. d. Water is used in hot water bottles for fomentation. Give reason for this. e. How is the kinetic energy of a moving cart affected if (i) its mass is doubled, (ii) its velocity is made equal to speed of light. [Ans: (i) if mass is doubled kinetic energy doubles. (ii) if velocity is made equal to speed of light the kinetic energy would be maximum] Question3. a. State two application of an echo. b. How does the resistance of a wire depend on its radius? Explain your answer. c. Why a fuse is always connected to the live wire in a circuit? d. State Snell s law of refraction. e. State the factors on which the deviation produced by a prism depends. Question4. a. State two differences between an electromagnet and a permanent magnet. b. On what factors does the resistivity of a wire depend? c. State two properties which are common to both beta rays and cathode rays. d. Draw a ray diagram of an image formed by slide projector. Question5. a. What do you understand by the conservation of mechanical energy? b. Name a machine which is used to: (i) multiply force, (ii) multiply speed, and (iii) change the direction of force applied. c. A block and tackle system has the velocity ratio 3. A man can exert a pull of 200 kgf. What is the maximum load he can raise with this pulley system if its efficiency is 60%? [Ans: 360kgf] Question6. a. What is a prism? With the help of a diagram of a prism, indicate its refracting surfaces, refracting edge and base. b. Explain the working of dual switch with a neat diagram. c. A boy of mass 40 kg runs up a flight of 15 steps, each 15 cm high in 10 s. Find the work done and the power developed by him. [Take g = 10 Nkg 1]. [Ans: 900J; 90W] Question7. 1. Define the term critical angle and total internal reflection. State two conditions necessary for total internal reflection to occur. Write down the relation for the critical angle in terms of refractive index. 2. Why do the qualities of sound of the same pitch differ when produced by different instruments? 3. A large truck & a car both moving with a speed v have ahead of collision and both of them come to halt after that, if the collision lasts for 10sec. i. Which vehicle experiences the greater force of impact? ii. Which vehicle experiences the greater momentum change? iii. Which vehicle experiences the greater acceleration? iv. Why is the truck likely to suffer more damage than the car? Question8. a. A bucket containing 8 kg of water at 25 C. 2 kg of water at 80 C is poured into it. Neglecting the heat energy absorbed by the bucket, calculate the final temperature of water. [Ans: 36 C] b. Why is the base of a cooking pan made thick and heavy? c. State with reason, which of the two, boiling water or steam both at 100 C will produce more severe burns. Question9. a. Differentiate between the e.m.f. and terminal voltage of a cell. b. An electric iron is rated at 750 W, 230 V. Calculate the electrical energy consumed by the iron in 16 hours. If the cost of electricity is Rs.5 per unit, calculate the total cost. [Ans: 12kWh; 60] c. State four main ways by which the speed of rotation of an electric motor can be increased. Question10. (a). (i) A machine raises a load of 750 N through a height of 16 m in 5 seconds. Calculate the power at which the machine works. [Ans: 2400W] (ii) State the principle of conservation of energy. (b). (i) A cook uses a 'fire tong' of length 28 cm to lift a piece of burning coal of mass 250 g. If he applies his effort at a distance of 7 cm from the fulcrum, what is the effort in S.I. unit? Take g = 10 m/s2. [Ans: 10N] (ii) State the S.I. unit of the momentum of a body. [Ans: kgm/s] (c). (i) The work done by the heart is 1 Joule per beat. Calculate the power of the heart if it beats 72 times in one minute. [Ans: 1.2W] (ii) Mention two properties of a wave: one property which varies and the other which remains constant when the wave passes from one medium to another. (d). (i) In the diagram given below, a ray of light PQ is incident normally on one face AB of an equilateral glass prism. What are the angles of incidence at the faces AB and AC? [Ans: AB=0 ; AC=60 ] (ii) Complete the ray diagram showing its emergence into air after passing through the prism. (e) An erect, diminished and virtual image is formed when an object is placed between the optical centre and principal focus of a lens. (i) Name the type of lens, which forms the above image. (ii) Draw a ray diagram to show the formation of the image with the above characteristics. (f) (i) Two friends were playing on their identical guitars whose strings were adjusted to give notes of the same pitch. Will the quality of the two notes be the same? Give a reason for your answer. (ii) Give the relation wavelength, time-period and wave-velocity of a wave. [Ans: v = ] t (g) (i)Why does the temperature of the surroundings start falling when the ice of a frozen lake starts melting? (ii) Four resistances of 2.0 each are joined end to end to form a square ABCD. Calculate the equivalent resistance of the combination between any two adjacent corners. [Ans: 1.5 ] (h). (i) In a three-pin plug, why is the earth pin made longer and thicker than the other two pins? (ii)What is meant by the statement, 'the critical angle of diamond is 24 '? (i). (i) How is the critical angle of a material related to its refractive index? [ =1/sinc] (ii) State the law of conservation of energy. (iii) Name the chief energy transformation that occurs: 1. in a Loudspeaker; 2. in an Electrical cell (Primary). (j). (i) The diagram shows a point source of light S, a convex lens L and a plane mirror M. These are placed such that rays of light, from S return to it after reflection from M. 1.What is the distance OS called? 2. To which point (left of S, on S, or right of S) will the rays return, if M is moved to the left and brought in contact with L? (ii) Copy the diagram of the forearm given below; indicate positions of Load, Effort and Fulcrum. Question11. (a) Define: (i) Work (ii) Power and (iii) Energy. (b) How is work done related to the applied force? (c) By what factor does the kinetic energy of a moving body change when its speed is reduced to half? (d) What do the following units measure: (i) Pascal. (ii) Kilowatt hour. (e) From the ground floor, a man comes up to the fourth floor of a building using the staircase. Another person comes up to the same floor using an elevator. Neglecting friction, compare the work done in the two cases. Question12. (a) Define specific heat capacity of a substance. State its S.I. unit. (b) Give one example each where high specific heat capacity of water is used: (i) In cooling. (ii) As heat reservoir. Question13. (a) Draw a ray diagram to illustrate the action of a convergent lens as a reading lens or a magnifying glass. (b)A prism deviates a monochromatic ray of light through an angle ' ' when the angle of incidence at the surface of the prism is 'i'. (i)Draw a graph showing the variation of ' ' with 'i'. On Your graph show the angle of minimum deviation. (ii) What is the relation between the angle of incidence and the angle of emergence when the ray suffers minimum deviation? (c). (i) Two isosceles right-angled prisms are arranged as shown in the figure. Copy the diagram and complete the path of the ray AB along which it passes through the prisms and comes out. (ii) Name the phenomenon being displayed by the path of the ray in the diagram. Question14. (a) The rear view mirror of a motor bike starts vibrating violently at some particular speed of the motor bike. (i)Why does this happen? (ii)What is the name of the phenomenon taking place? (iii)What could be done to stop the violent vibrations? (b) A sound wave of wavelength 0.332 m has a time period of 10-3 s. If the time period is decreased to 10-4 s; calculate the wavelength and frequency of the new wave. [Ans: 332 x 10 4m; 104s] (c) (i) Define the terms: Amplitude and frequency for sound waves. (ii) Name the subjective property of sound related to its frequency and of light related to its wavelength. Question15. (a) A radar is able to detect the reflected waves from an enemy aeroplane, after a time interval of 0.02 milliseconds. If the velocity of the waves is 3 108 ms-1, calculate the distance of the plane from the radar. [3km] (b) A piece of ice is heated at a constant rate. The variation of temperature with heat input is shown in the graph below: (i) What are represented by AB and CD? (ii)What conclusion can you draw regarding the nature of ice from the alongside graph? (c) If there is no heat loss to the surroundings, the heat released by the condensation of m2g of ice at, 0 C into water at 0 C. Find: (i) the heat lost by steam in terms of m1 (ii) the heat gained by ice in terms of m2. (iii). Form a heat equation and find the ratio of m2: m1 from it. (Specific latent heat of vaporization of steam = 2268 kJ/kg; Specific latent heat of fusion of ice = 336 kJ/kg. Specific heat capacity of water = 4200 J/kg C). Question16. (a). An electrical appliance is rated 1500 W, 250 V. This appliance is connected to 250 V mains. Calculate: (i) the current drawn. (ii) the electrical energy consumed in 60 hours. (iii) the cost of electrical energy consumed at Rs. 4.50 per kWh. [Ans: (i) 6A; (ii) 90kWh; (iii) 405] (b). A monochromatic point source of light 'O' is seen through a rectangular glass block ABCD. Paths of two rays, in and outside the block, are shown in the figure below. (i) Does the source 'O' appear to be nearer or farther with respect to the surface AB? (ii) How does the shift depend on the thickness (AD or BC) of the block? (iii) Justify your answer in (ii) with the help of an appropriate ray diagram. (iv) For the same rectangular glass block, which colour from the visible spectra will produce the maximum shift? (c). In the figure given alongside, A, B and C are three ammeters. The ammeter B reads 0.5A. (All the ammeters have negligible resistance.) Calculate: (i) the readings in the ammeters A and C. (ii) the total resistance of the circuit [Ans: (i) A=1.5A; C=1A; (ii) 4 ] Modern Physics Question1. What are , and radiations composed of? Question2. What is thermionic emission? Name two factors on which thermionic emission depends. Question3. An alpha particle absorbs an electron. What does it change to? Question4. An atomic nucleus denoted by AZ X emits an alpha particle. Write an equation to show the formation of the daughter product. Question5. (i) A thorium isotope 223 undergoes an decay and 90Th changes into Radium. What is the atomic number and mass number of the radium produced? (ii) If the radium undergoes a further disintegration and emits two beta particles, represent this reaction in the form of an equation. (iii) What is the source of energy released during the decay? Question6. A radioactive nucleus AZ X first emits a beta particle and then an alpha particle and the resulting nucleus is represented by QPY . What are the values of P and Q in terms of A and Z? Question7. What is radioactivity? Question8. A radioactive substance is oxidized. What change would you expect to take place in the nature of the radioactivity? Give a reason for your answer. Question9. Explain what changes take place within the nuclei, when beta particles are emitted by a radioactive substance? Question10. Name the particles given out during radioactive decay. Question11. Show by equations, the effect on the proton number Z and the mass number A of the parent nucleus brought about by the two types of radioactive decay. Question12. 27 12 Mg Al . (i) 27 emits a beta particle and is transformed into aluminium. Write 12 Mg the mass number and the atomic number of aluminium. (ii) Aluminium emits a gamma ray. What is the resulting nucleus? Question13. Which radiation or particle from radioactive decay produces maximum biological damage? Question .14. State three precautions that must be taken while handling a radioactive source. Question .15. An element X changes into another element Y with the emission of beta particle. Write down the equation showing the changes in the nucleus. Take the proton number of X as Z and mass number as A respectively. Question .16. Describe briefly, two properties each of alpha and gamma radiations. Question .17. A mass of lead is embedded in a block of aluminium. Radiations from a radioactive source incident on the side of the block produce a shadow on a fluorescent screen placed beyond the block. The shadow of aluminium is faint but the shadow of lead is dark. Give reason for this difference. Question .18. The isotope of uranium 238 decay by alpha emission to 92U an isotope of thorium (Th). The thorium isotope decay by beta emission to an isotope of Protactinium (Pa). Write down the equations to represent these two nuclear changes. Question .19. Define the term work function of a metal. Question .20. Mention two common properties of gamma radiations and visible light. Question .21. State one use of radioisotopes. Question .22. Why are materials of low work function preferred as thermionic cathode materials? Question .23. A certain radioactive nucleus emits a particle that leaves its mass unchanged but increases its atomic number by one. Identify the particle and write its symbol. Question .24. (i) Define thermionic emission. (ii) Mention one use of thermionic emission. (iii) Name a substance which is a good thermionic emitter. Question .25. State three properties that is common to and shown by both beta rays and cathode rays. Question .26. What will an alpha particle change into when it absorbs: (i) One electron. (ii) Two electrons? Question .27. Mention two important properties of a metal that make it a good thermionic emitter. Question .28. (i) What happens to the atomic number of an element when it emits: (1). an alpha particle and (2). a beta particle. (ii) Explain why alpha and beta particles are deflected in an electric or a magnetic field but gamma rays are not deflected in such a field. Question. 29. (i) What is thermionic emission. (ii) Name two factors on which the rates of emission of thermions depend. Question. 30. What is an isotope? One isotope of uranium has a mass number of 235 and an atomic number of 92. (i) What is the number of electrons in a neutral atom of this isotope? (ii) How many protons are there in the nucleus of this atom? (iii) What is the number of neutrons in the nucleus of this isotope? (iv) Do all the isotopes of uranium have the same number of neutrons. (v) What is the number of protons in U238 ? Question. 31. Ultraviolet light falls on a dry zinc plate. (i) Name the particles emitted from the plate. (ii) What is the nature of charge acquired by the plate. (iii) Name the phenomenon that takes place. (iv) Name one of the devices based upon the above phenomenon. Question. 32. State the mechanism of production of X rays. Give two important properties of X ray. Question. 33. What is the photoelectric effect ? Draw a neat labelled diagram of a photoelectric cell. (out of course) Question. 34. (i) Define nuclear fusion and state the necessary conditions for the same. (ii) Name two factors on which the rates of emission of thermions depend. Question. 38. An particle absorbs an electron. What does it change to ? Question. 39. A fission reaction is represented as follows : 2 2 4 1H + 1H --> 2He + x. Identify x. Question.40. (i) Draw a neat labelled diagram of a hot cathode ray tube. (ii) What is the effect on the beam particles if: (a) a hotter filament is used ? (b) the anode voltage is increased ? (iii) Name one device in which the cathode ray tube is used. Question.41. State the factors that affect the rate of emission of electrons in a photoelectric cell. Question.42. (i) A thorium isotope 223 undergoes an decay and 90Th changes to radium. What is the atomic number and mass number of radium produced? (ii) If the radium undergoes a further disintegration and emits two particles, represent the reaction in the form of an equation. (iii) What is the source of energy released during the decay ? Question.43. In the nuclear reaction given below, nucleus X changes to 226 another nucleus Y. Y + + energy. 88 X (i) What are the atomic and mass numbers of Y ? (ii) Name the gas formed when the -particle acquires two electrons. (iii) What is the effect on the motion of the -particle when it passes through a region containing a magnetic field ? Question.45. What is the main difference between fission reaction and fusion reaction ? Give one example of each. Question.46. An atomic nucleus denoted by AZ X emits an alpha particle. Write an equation to show the formation of the daughter product. Question. 49. a radioactive element X first emits a particle and then an alpha particle and the resulting nucleus can be represented QPY . What are the value of P and Q in terms of A and Z ? Question. 50. (i) What is nuclear fusion ? (ii) name the particles which cause nuclear fission of U-235. Question. 52. What is radioactivity ? Question. 53. A radioactive substance is oxidized. What change would you expect to take place in the nature of its radioactivity ? Give a reason for your answer. Question. 54. What are beta rays and gamma rays ? Question. 55. Explain briefly what change takes place within the nuclei, when beta particles are emitted by a radioactive substance. Question. 56. Name the particles given out during radioactive decay. Question. 57. Show by equations, the effect on the proton number Z and mass-number A of the parent nucleus brought about by the two types of radioactive decay. Question. 58. What is Carbon-14-dating ? Question. 59. The following diagram is of the simplified version of an electron-gun which is an integral part of a cathode ray-tube, A is a filament and B is a metal cylinder . (i) Copy the diagram in your answer book. Draw a pair of plates P1 and P2 to apply electric field, a screen S and an enclosure. (ii) What are the functions of A, B, P1, and P2 ? Question. 61. State three precautions that must be taken while handling a radioactive source. Question. 62. Mention two possible sources of background radiation. Question. 63. An element X changes to another element Y with the emission of beta particles. Write down the equation showing changes in the nucleus. Take the proton number and mass number of X as Z and A respectively. Question. 64. State briefly two uses of cathode ray tube. Question. 65. Name the technique used to estimate the age of very old trees, plants, wood and other such specimens. Name the isotope that forms the basis of this technique. [Carbon C dating; 14 6 Question. 67. A mass of lead is embedded in a block of aluminium (2 mm thick). Radiations from a radioactive source incident on the side of the block produce a shadow on a fluorescent screen placed beyond the block. The shadow of the block of aluminium is fainter than the shadow of lead. Give the reason for this difference. Question. 68. (i) State two factors on which the rate of emission of thermions depends. (ii)The isotope of 238 92U decays by alpha emission to an isotope of Thorium (Th). The thorium isotope decays by beta emission to an isotope of Protactinium (Pa). Write down the equations to represent these two nuclear changes. (iii) Draw a cathode ray tube consisting of a heater, a cathode, a cylindrical anode and a deflecting system. Show how you will connect a low tension battery of 6 V and a high tension one of 1000 v to the electrodes of the tube. Question. 69. (i) Define the term work function of a metal. (ii) Mention two common properties of gamma radiations and visible light. Question. 70. How many alpha and beta particles are emitted when 206 uranium 238 92U decays to lead 82 Pb ? Question. 71. (a) (i) Copy and complete the above diagram by showing and labelling the paths of alpha, beta and gamma radiations in an electric field. (ii) Name the radiations which have the least penetrating power. (b) (i) Give one difference between a chemical change and a nuclear change. (ii) How is a cathode ray tube used to convert an electrical signal into a visual signal? (c) Copy and complete the following nuclear equations by filling the correct values in the blanks: 238 .. .. .. P P P P 92 .. 1 .. 2 .. 3 Question. 74. (i) Mention two important precautions that should be taken while handling radioactive materials. (ii) State one use of radio-isotopes. Question. 75. (i) Draw a labelled diagram of a hot cathode ray tube. (ii) Why are the materials of low work function preferred as thermionic cathode materials ? Question. 83. Name the three main parts of a cathode ray tube. Mention one important function of each of the three main parts. Heat Question .1. Question .2. Which material is the calorimeter commonly made of? Question .3. Give two reasons as to why copper is preferred over other metals for making calorimeter. Question .4. Define the term specific heat capacity of a substance. Give its SI unit. Question .5. Define specific latent heat of fusion of ice. Give its SI unit. Question .6. Explain briefly: Why hot water bottles are very efficient for fomentation? Question .7. What is the effect of increase in pressure on the melting point of ice and boiling point of water? Question .8. Explain why bottled soft drinks are more effectively cooled by cubes of ice than by ice water. Question .9. Explain why the surroundings become pleasantly warm when water in a lake starts freezing in cold countries. Question .10. If, in a central heating system, steam enters a radiator pipe at 100 C and water leaves the radiator pipe at 100 C, Which radiator pipe heat a room? Give an explanation for your answer. Question .11. It takes a much longer time to boil off (change to steam) a certain quantity of water, rather than to bring it to its boiling point from room temperature, say 25 C. Explain the reason for this. Question .12. Explain why one feels ice cream at 0 C colder than water at 0 C. Question .13. Give one example of each where high specific heat capacity of water is used (i) in cooling and (ii) as heat reservoir. OR Explain why water is used in hot water bottles for fomentation and also as a universal coolant. Question .14. Does land cool at a slower or faster rate than water? Give one reason for your answer. Question .15. Explain why steam pipes warm a building more effectively than hot water pipes in cold countries. Question .16. In winter, the weather forecast for a certain day was severe frost . A wise farmer watered his fields the night before to prevent frost damage to his crops. Why did he water his fields? Question .17. State the principle of Calorimetry. Or. What is the principle of Calorimetry? Question .18. Which of the two , 1 g of ice at 0 C or 1 g of water at 0 C contains more heat? Give reason for your answer. Question .19. Why are burns caused by steam more severe than those caused by boiling water at the same temperature? Question .20. Why does the heat supplied to a substance during its change of state not cause any rise in its temperature? Question. 21. Does the boiling point of water changes with altitude ? If so how? Question. 22. Define specific latent heat of vaporisation. Question. 23. Which material is the calorimeter commonly made of ? Question. 24. 1 kg of ice at 0 C is being continuously heated through an electric heater of 1kW. Assuming that all the heat is transmitted to ice, calculate the time interval in second for : (i) ice to completely melt to water at 0 C. (ii) water to get heated from 0 C to 100 C. (iii) water at 100 C to convert into steam. [Given : Specific latent heat of ice= 3,36,000 J kg-1K-1 Specific heat capacity of water = 4,2200 J kg-1 K-1 Specific latent heat of steam = 22,60,000 J kg-1 K-1] [Ans. (i) 336 s (ii) 420 s (iii) 2,260 s.] Question. 25. A given liquid changes into the gaseous state at a fixed temperature as well as at all temperatures. (i) Name the process that takes place in each of the above two cases. (ii) Mention two points of difference between the two cases in (i) above. Question. 26. (i) Define the term specific heat capacity of a substance. Give its SI unit. (ii) A 30 g ice cube at 0 C is dropped into 200 g of water at 30 C. Calculate the final temperature of water when all the ice cube has melted. Given : Latent heat of ice = 80 cal g-1; Specific heat capacity of water = 1 cal g-1 C-1 Ans. 15.65 C. Question. 27. Explain how the following factors affect the rate of evaporation of a liquid : (i) Temperature of the liquid. (ii) Area of the exposed surface. (iii) Moisture in the surrounding air. Question. 28. Define specific latent heat of fusion of ice. Give its SI unit. Question. 29. What is the effect of increase in pressure on the melting point of ice and boiling point of water ? Question. 30. A piece of metal at 10 C has a mass of 50 g. When it is immersed in a current of steam at 100 C, 0.7 g of steam is condensed on it. Calculate the specific heat of metal. [Given : Latent heat of steam = 540 cal/g] [Ans. 0.084 cal g-1 C-1 ] Question. 31. Explain briefly: (i) Why hot bottles are very efficient for fomentation ? (ii) How human body temperature is maintained at normal value(37 C) when the atmospheric temperature rises as high as 45 C ? Question. 32. State two ways, other than direct heating, by which a given quantity of liquid can be made to evaporate more quickly. Question. 33. The temperature recorded by a thermometer decreases when its bulb is covered with a piece of cloth soaked in sprit. Explain why. Question. 34. 2 kg of ice melts when a jet of steam at 100 C is passed through a hole drilled in a block of ice. What mass of steam was used ? [Given : Specific heat capacity of water = 4,200 J/ kg C. Specific latent heat of fusion of ice = 336 103 J/kg. Specific latent heat of vaporisation = 2,268 103 J/kg. ] Ans. 0.25 kg Question. 35. Why does evaporation always produce cooling ? Question. 36. Explain why the surroundings become pleasantly warm when water in the lake starts freezing in cold countries. Question. 38. The graph represents a cooling curve for a substance being cooled from higher temperature to a lower temperature. (i) What is the boiling point of the substance ? (ii) What happened to the region DE ? (iii) Why is region DE shorter than the region BC ? Question. 39. At what approximate temperature will water boil in a pressure cooker? Question. 40. Explain why bottled soft drink are more effectively cooled by cubes of ice than by ice water. Question. 41. 10 g of ice of 0 C absorbed 5,460 J of heat to melt and change into water at 50 C. Calculate the specific latent heat of fusion of ice. Given specific heat capacity of water is 4,200 J kg-1 C-1. Ans. 3,36,000 J Question. 44. A hot solid of mass 60 g at 100 C is placed in 100 g of water at 18 C. The final steady temperature recorded is 20 C. Find the specific heat capacity of the solid. Ans. 0.04 cal/g C. Question. 42. In an experiment to determine the specific latent heat of vaporisation of steam L, the following measurements were taken: Mass of calorimeter + stirrer = x kg Mass of water = y kg Initial temperature of water = t1 C Final temperature of mixture = t2 C Given: S.H.C. of calorimeter and water are S1 and S2 respectively. Express L in terms of above data. Mass of condensity (steam condensed) = M kg. Question. 44. (i) Calculate the mass of steam at 100 Cthat must be passed into 8.4 kg of water at 30 C to raise the temperature of water to 80 C. Ans. 750 g. (ii) Why does the surrounding become pleasantly warm when freezing starts in cold countries? Question. 45. In a laboratory experiment to measure specific heat capacity of copper, 0.02 kg of water at 70 C was poured into a copper calorimeter with a stirrer of mass 0.16 kg initially at 15 C. After stirring, the final temperature reached to 45 C. Specific heat of water is taken as 4200 J/kg C. (i) What is the quantity of heat released per kg of water per 1 C fall in temperature? (ii) Calculate the heat energy released by water in the experiment in cooling from 70 C to 45 C. (iii) Assuming that the heat released by water is entirely used to raise the temperature of calorimeter from 15 C to 45 C, calculate the specific heat capacity of copper. Ans. (i) 42000 J kg-1 C-1, (ii) 2100 J, (iii) 437.5 J/kg C. Question. 46. A vessel of negligible heat capacity contains 40 g of ice in it at 0 C. 8 g of steam at 100 C is passed into the ice to melt it. Find the final temperature of contents of the vessel. [Specific latent heat of vaporisation of steam = 2268 J/g, Specific latent heat of fusion of ice = 336 J/g, Specific heat capacity of water = 4.2 J/g] Ans. 40 C. Question. 47. (i) Define specific heat capacity of a substance. State its SI unit. (ii)Give one example each where high specific heat capacity of water is used: (a) in cooling. (b) as a reservoir. Question. 48. (i) Does land cool at a slower or faster rate than water? Give one reason for your answer. (ii) Explain why steam pipes warm a building more effectively than hot water pipes in cold countries. Question. 49. In a laboratory experiment for finding specific latent heat of ice, 100 g of water at 30 C was taken in calorimeter made of copper and of mass 10 g. When 10 g of ice at 0 C was added to the mixture and kept within the liquid till the ice melted completely, the final temperature of the mixture was found to be 20 C. (i) What is the total quantity of water in the calorimeter at 20 C? (ii) Specific heat capacity of water and copper being 4.2 J/g C and 0.4 J/g C respectively, what quantity of heat would each release in cooling down to 20 C from the initial stage ? (iii) Write an expression for the heat gained by ice on melting. (iv) Calculate the value of the latent heat of fusion of ice from the data discussed above. Ans. (i) 110 g, (ii) 40 J, (iii) {10 L + 840} J, (iv) 340 103 J/kg. Question. 50. (i) In winter, the weather forecast for a certain day was severe frost . A wise farmer watered his fields the night before to prevent frost damage to his crops. Why did he water his fields? (ii) 10125 J of heat energy boils off 4.5 g of water at 100 C to steam at 100 C. Find the specific latent heat of steam. Ans. 2250 J/g. Question. 51. (a) A thermos flask of negligible heat capacity contains 100 g of ice and 30 g of water. (i) Calculate: (1) the mass of steam at 100 C needed to condense in the flask so as to just melt the ice (2) the amount of water in the flask after condensation. [Specific latent heat of vaporisation of steam = 2260 J/g. Specific latent heat of fusion of ice = 336 J/g. Specific heat capacity of water = 4.2 J/g C] Ans. (a) 12.537 g (b) 142.537g. (ii) Is it possible to condense the water formed, back to ice by adding ice at 0 C? Explain, giving a suitable reason to justify your answer. (b) (i) State the Principle of Calorimetry. (ii) Express 1 kW h in terms of S.I. unit of energy. Ans. 3.6 105 J. (iii) Which of the two, 1 g of ice at 0 C or 1 g of water at 0 C contains more heat ? Give a reason for your answer. Question. 52. Why does the temperature of the surroundings start falling when the ice of a frozen lake starts melting? Question. 53. Calculate the heat energy that will be released when 5 kg of steam at 100 C condenses to form water at 100 C . Express your answer in S.I. unit. (Specific latent heat of vaporisation of steam is 2268 kJ/kg). [Ans. 11340 kJ] Question. 54. Give two reasons as to why copper is preferred over other metals for making calorimeter. Question. 55. Water falls from the height of 50 m. Calculate the rise in temperature of water when it strikes the bottom. [g = 10 ms-2, specific heat capacity of water = 4200 Jkg-1 C-1] Ans. 0.12 C Question. 56. A piece of ice is heated at a constant rate. The variation of temperature with the heat input is shown in the graph below: (i) What are represented by AB and CD? (ii) What conclusion can you draw regarding the nature of ice from the graph? Question. 57. If there is no heat loss to the surroundings, the heat released by the condensation of m1 g of steam at 100 C into water at 100 C can be used to convert m2 g of ice at 0 C into water at 0 C. (i) Find: [1] the heat lost by steam in terms of m1. [2] the heat gained by ice in terms of m2. (ii) Form a heat equation and find the ratio of m2: m1 from it. [Specific latent heat of vaporisation of steam = 2268 kJ/kg, Specific latent heat of fusion of ice = 336 kJ/kg, Specific heat capacity of water = 4200 J/kg C.] Ans. (i){1} 2688m1 J, {2} 336m2 J. (ii) m2 : m1 = 8 : 1 Question. 58. Calculate the amount of heat released when 5 g of water at 20 C is changed into ice at 0 C. Specific heat capacity of water = 4.2 J/g C, specific latent heat of fusion of ice = 336 J/g. Ans. 2100 J Question. 59. A piece of iron of mass 2 kg has a thermal capacity of 966 J/ C. (i) How much heat is needed to warm it by 15 C? (ii) What is its specific heat capacity in S.I. units? Ans. (i) 14490 J, (ii) 483 J/kg C Question. 60. (i) Define specific latent heat of vaporisation of a substance. (ii) What is the principle of Calorimetry? Question. 61. Explain why water is used in hot water bottles for fomentation and also as a universal coolant. Question. 62. Some hot water was added to three times its mass of cold water at 10 C and the resulting temperature was found to be 20 C. What was the temperature of the hot water? Ans. 50 C. Question. 63. Why are burns caused by steam more severe than those caused by boiling water at the same temperature? Question. 64. (i) What is meant by specific heat capacity of a substance? (ii) Why does the heat supplied to a substance during its change of state not cause any rise in its temperature? Question. 65. A substance is in the form of a solid at 0 C. The amount of heat added to this substance and the temperature of the substance are plotted on the following graph : If the specific heat capacity of the solid substance is 500 J/kg C, find from the graph: (i) The mass of the substance; (ii) the specific latent heat of fusion of the substance in the liquid state. Question. 66. Some hot water was added to three times its mass of cold water at 10 C and the resulting temperature was found to be 20 C. What was the temperature of the hot water? Question. 67. A piece of iron of mass 2.0 kg has a thermal capacity of 966J/ C. (i) How much heat is needed to warm it by 15 C? (ii) What is its specific heat capacity in S.I. units? Question. 68. Calculate the amount of heat released when 5.0 g of water at 20 C is changed into ice at 0 C. Specific heat capacity of water = 4.2 J/g C, specific latent heat of fusion of ice = 336 J/g C. Question. 69. m1 g of steam at 100 C is condensed to form water at 100 C. If there is no heat loss to the surroundings, the heat released in this process is used to convert m2 g of ice at 0 C into water at 0 C. Find: (i) The heat lost by steam in terms of m1. (ii) The heat gained by ice in terms of m2. (iii) Form a heat equation and find the ratio of m2: m1 from it. (Specific latent heat of vaporization of steam = 2268 kJkg-1; Specific latent heat of fusion of ice = 336 kJkg-1; Specific heat capacity of water = 4200 Jkg-1 C-1). Question. 70. Calculate the heat energy that will be released when 5.0 kg of steam at 100 C condenses to form water at 100 C. Express your answer in SI unit. (Specific latent heat of vaporization of steam is 2268 kJkg-1) Question. 71. A thermos flask of negligible heat capacity contains 100 g of ice and 30 g of water. Calculate: (i) the mass of steam at 100 C needed to condense in the flask so as to just melt the ice. (ii) the amount of water in the flask after condensation. (Specific latent heat of vaporization of steam = 2260 Jg-1, Specific latent heat of fusion of ice = 336 J/g, Specific heat capacity of water = 4.2 J/g C). (iii) Is it possible to condense the water formed, back to ice by adding ice at 0 C? Explain giving a suitable reason to justify your answer. Question. 72. 10125 J of heat energy boils off 4.5 g of water at 100 C to steam at 100 C. Find the specific latent heat of steam. Question. 73. In a laboratory experiment for finding the specific latent heat of ice, 100 g of water at 30 C was taken in a calorimeter made of copper and mass 10 g. When 10 g of ice at 0 C was added to the mixture and kept within the liquid till the ice melted completely, the final temperature of the mixture was found to be 20 C: (i) what is the total quantity of water in the calorimeter at 20 C. (ii) Specific heat capacities of water and copper being 4.2 J g C-1 and 0.4 J g respectively, what quantity of heat would each release in cooling down to 20 C from the initial stage? (iii) Write an expression for the heat gained by ice on melting. (iv) Calculate the value of the latent heat of fusion of ice from the data discussed above. Question. 74. A vessel of negligible heat capacity contains 60 g of ice in it at 0 C. 8 g of steam at 100 C is passed into the ice to melt it. Find the final temperature of the contents of the vessel (specific latent heat of fusion of ice = 336 Jg-1, specific heat capacity of water = 4.2J/g C). Question. 75. In a laboratory experiment to measure specific heat capacity of copper, 0.02 kg of water at 70 C was poured into a copper calorimeter with a stirrer of mass 0.16 kg initially at 15 C. After stirring the final temperature reached to 45 C. Specific heat of water is taken as 4200 J/kg C. (i) What is the quantity of heat released per kg of water per 1 C fall in temperature? (ii) Calculate the heat energy released by water in the experiment in cooling from 70 C to 45 C. (iii) Assuming that the heat released by water is entirely used to raise the temperature of calorimeter from 15 C to 45 C, calculate the specific heat capacity of copper. Question. 76. A hot solid of mass 60 g at 100 C is placed in 100 g of water at 18 C. The final steady temperature recorded is 20 C. Find the specific heat capacity of the solid. Question. 77. 2 kg of ice melts when a jet of steam at 100 C is passed through a hole drilled in a block of ice. What mass of steam was used? Given: Specific heat capacity of water = 4,200 J/kg C, Specific latent heat of fusion of ice = 336 103 J/kg, Specific latent heat of vaporization of steam = 2,268 103 J/kg. Question. 78. 10 g of ice at 0 C absorbed 5,460 J of heat to melt and change into water at 50 C. Calculate the specific latent heat of fusion of ice. Given specific heat capacity of water is 4,200 J/kg C. Question. 79. A piece of metal at 10 C has a mass of 50 g. When it is immersed in a current of steam at 100 C, 0.7 g of steam is condensed on it. Calculate the specific heat of the metal. Given Latent heat of steam = 540 cal/g. Question. 80. A 30 g ice cube at 0 C is dropped into 200 g of water at 30 C. Calculate the final temperature of water when the entire ice cube has melted. Given: Latent heat of ice = 80 cal/g; specific heat capacity of water = 1 cal/g C. Question. 81. 1 kg of ice at 0 C is being continuously heated through an electric heater of 1 kW. Assuming that all the heat is transmitted to ice, calculate the time interval in second for: (i) ice to completely melt to water at 0 C. (ii) water to get heated from 0 C to 100 C, (iii) water at 100 C to convert into steam. [Given: Specific latent heat of ice = 3, 36,000 J/kg, Specific heat capacity of water = 4,200 J/kg K, Specific latent heat of steam = 22, 60,000 J/kg.] Question. 82. A metal of mass 250 g is heated to a temperature of 65 C. It is then placed in 50 g of water at 20 C. The final steady temperature of water becomes 25 C. Neglecting the heat taken by the container, calculate the specific heat capacity of the metal. Electromagnetism Question .1. Describe the construction and working of a simple step-up transformer. Or What is the function of a step-up transformer? Question .2. Name the principle on which the functioning of a transformer depends? Question .3. Can a transformer work when it is connected to a dc source? Question .4. (i) Draw a neat labelled diagram of an ac generator. (ii) What is the magnitude of e.m.f induced in the coil when its plane becomes parallel to the magnetic field? (iii) State two ways by which the e.m.f in an ac generator can be increased. Question .5. State two ways of increasing the speed of a dc motor. Question .6. State the energy transformations taking place in the following: (i) electric cell. (ii) electric generator. Question .7. (i) Draw a labelled diagram of the device you would use to transform 200 V ac to 15 V ac. (ii) What is the name of this device? Or Draw a labelled diagram to show the various components of a step down transformer. Question .8. What is an electromagnet? State two ways in which, the strength of an electromagnet can be increased. Question .9. State two characteristics of a primary coil of a step-up transformer when compared to the secondary coil. Question .10. With reference to the dc motor, State: (i) the energy change that takes place. (ii) the principle on which it operates. Question .11. (a) Draw a representative diagram of a dc motor. Label the following in your diagram: (i) the field magnet. (ii) the armature. (iii) commutator. (iv) brushes. What is the energy changes involved in this case? (b) State the function of the split ring. Question .12. Draw a sketch of an electric bell with electrical connections and label the main parts. Why the armature is made of soft iron and not steel? Question .13. State the main difference between a step-up and step-down transformer. Question .14. Explain briefly how a magnet can be demagnetized using an alternating current. Question .15. State the energy change which takes place when a magnet is moved inside a coil having a galvanometer at its ends. Name this phenomenon. Question .16. Mention two reasons why a soft iron core is used within the coil of a moving coil galvanometer. Question .17. State two advantages of an electromagnet over a permanent magnet. Question .18. (i) What will happen to a compass needle when the compass is placed below a wire and a current is made to flow the wire? Give a reason to justify your answer. (ii) What energy conversion takes place during the working of a d.c. motor? Question.19. (i) State two factors on which the strength of an induced current depends. (ii) When a solenoid that is carrying current is freely suspended, it comes to rest along a particular direction. Why does this happen? (iii) What will be the effect on the working of an electric bell if instead of a direct current, an alternating current is used? Question. 20. Name the principle on which functioning of a transformer depends. Question. 21. What is the function of a step-up transformer? Question. 22. Can a transformer work when it is connected to a d. c. source? Question. 23. Diagram given below, shows schematically part of a stepdown transformer. Draw the complete diagram in your answer sheet. Question. 24. Diagram below shows a circuit containing a coil wound on a long and thin hollow cardboard tube. Copy the diagram. (i) Show the polarity acquired by each face of the solenoid. (ii) Draw the magnetic lines of force inside the coil and also show their directions. (iii) Mention two methods to increase the strength of the magnetic field inside the coil.. Question. 25. (i) Draw a neat labelled diagram of an a. c. generator. (ii) What is the magnitude of the e. m. f. induced in the coil when its plane becomes parallel to the magnetic field? Question. 26. The following diagram two straight wires carrying current. Copy the diagram and draw the pattern of lines of force around them and mark their directions. Question. 27. State two ways of increasing the speed of rotation of a d. c. motor. Question. 28. (i) Draw a labelled diagram of the device you would use to transform 200 volts a. c. to 15 volts a. c. (ii) What is the name of this device? Question. 29. What energy conversion takes place during the working of a d. c. motor? Question. 30. What is an electromagnet? State two ways by which the strength of an electromagnet can be increased. Question. 31. State two characteristics of a primary coil of a step-up transformer when compared to the secondary coil. Question. 32. With reference to a d. c. motor state: (i) The energy change that takes place. (ii) The principle on which it operates. Question. 33. Draw a representative diagram of a DC motor. Label the following in your diagram. (i) The field magnet. (ii) The armature. (iii) Commutator. (iv) Wire brushes. What is the energy change involved in this case? Question. 34. State two dissimilarities between a D.C. motor and an A.C. generator. Question. 35. State two advantages of an electromagnet over a bar magnet. Question. 36. Draw a sketch of an electric bell with electrical connections and label the main parts. Why the armature is made of soft iron and not steel? Question. 37(a) Draw a labelled diagram to show the various Components of a step-down transformer. (b) State the main difference between a step-up and step-down transformer. Question. 38. Explain briefly how a magnet can be demagnetized using an alternating current. Question. 39. State two ways by which the e.m.f in an A.C. generator can be increased. Question.40. The diagram shows a coil connected to a centre zero galvanometer G. The galvanometer shows a deflection to the right when the N-pole of a powerful magnet is moved to the right as (i) Explain why the deflection occurs in the galvanometer? (ii) Does the direction of the current in the coil appear clockwise or anticlockwise when viewed from the end A? (iii) State the observation in G when the coil is moved away from N. (iv) State the observation in G when, both the coil and the magnet, are moved to the right at the same speed. Question. 41. Name any two electromagnetic waves which have a frequency higher than that of violet light. State one use of each. Question. 42. State the energy change which takes place when a magnet is moved inside a coil having a galvanometer at its ends. Name this phenomenon. Question. 43. Draw a labelled diagram of an A.C. generator. Question. 44. State the function of a split ring in a d. c. motor. Question. 45. Mention two reasons why a soft iron core is used within the coil of a moving coil galvanometer. Question. 46. State two advantages of an electromagnet over a permanent magnet. Question. 47. What will happen to a compass needle when the compass is placed below a wire and a current is made to flow through the wire ? Give a reason to justify your answer. Electric Power and Household Electricity Question .1. What do you understand by 1 kilowatt hour? Question .2. An electric bulb has a filament and gases filled at low pressure. (i) What is the material commonly used for the filament? (ii) Name the gases used for filling the bulb. Question .3. Name the colour of the three core cable along with their corresponding electrical connections to a socket. Question .4. Which part of an electric appliance is earthed? Question .5. Define 1 watt and 1 kilowatt. Question .6. There are three pins in an electric plug top. Answer the following: (i) How would you identify the earth pin? (ii) In which of the three connecting wires should the electric switch be connected? (iii) Explain why a switch should not be touched with wet hands. Question .7. Give one example each of material suitable for making: (i) fuse wire and (ii) heater element. Question .8. Score off the incorrect and write correctly the following: In wiring a three pin plug, the brown sleeved wire is connected to the material/live pin and the green/ blue sleeved wire is connected to the metal body of the appliance. Question .9. You have just paid the electricity bill for your house. (i) what was it that your family consumed, for which you had to pay? (ii) In what unit was it measured? Question .10. What are high tension wires? Give two characteristics of these wires. Question .11. Why is the filament of an electric iron or kettle put between mica sheets? Question .12. Explain briefly how a fuse protects an electric circuit? Question .13. What is earthling? What is its use? Or What is meant by earthling of an electrical appliance? Why is it essential? Question .14. What is meant by earthling of an electrical appliance? How does earthling offer protection? Question .15. Name the material used for making fuse wire. State two properties of the material of fuse wire which make it suitable for use. Question .16. Under what circumstances does one get an electric shock from an electric appliance? Question .17. How does the power rating of a device help us to decide about the type of leads (connecting wires) to be used for that? Question .18. Explain briefly the function of the following in the household wiring: (i) a three pin plug and (ii) main switch. Question. 19. Make a table with names of 3 electrical appliances used in your home in one column, their power, voltage rating and approximate time for which each is used in one day in the other column. Question .20. Which of the two wires of similar dimension, copper or nichrome, would you use for the electric heater. Give reasons to justify your answer. Question .21. Two fuse wires of the same length are rated 5 A and 20 A. Which of the two fuse wires is thicker and why? Question .22. State the purpose of a fuse in an electric circuit. Name the material used for making a fuse wire. Question .23. Electric power P is given by the expression P = (Q V) (i) What do the symbol Q and V represent? (ii) Express power in terms of current and resistance explaining the symbols used their in. Question .24. In a three-pin plug, why is the earth pin made longer and thicker than the other two pins? Question .25. Draw a labelled diagram of a three-pin socket. Question .26. Of the three connecting wires in a household circuit: (i) Which two of the three wires are at the same potential? (ii) In which of the three wires should the switch be connected? Question. 27. An electric heater is rated 500 kVA, 220 V. If the heater is operated for 1 hour, calculate the energy consumed: (i) in kWh and (ii) in joule. Question. 28. Convert 1 kWh into joule. Question. 29. An electric bulb is marked 220V 100 W. The bulb is connected to a 220 V supply. (i) Calculate (a) the resistance of the filament. (b) Current flowing through the filament. (ii) is the filament resistance of the glowing bulb greater, smaller or same as compared to its resistance when it is not glowing? Question. 30. A refrigerator is marked 80 W, 220 V. (i) How much energy does it consume in one day if on an average it is used for 20 hours a day? (ii) What is likely to happen if the voltage drops to 50 V.? Question. 31. What quantity of heat will be produced in a coil of resistance 80 ohm if current of 3 A is passed through it for 4 second. Question. 32. Calculate the electrical energy in SI units consumed by a 100 W bulb and a 60 W fan connected in parallel in 5 minutes. Question. 33. A family uses a light bulb of 100 W, a fan of 100 W and an electric heater of 1000 W each for 8 hours daily. If the cost of electricity is Rs2.00 per unit, what is the expenditure for the family per day on electricity? Question. 34. A bulb is marked 100 W, 220 V and an electric heater is marked 2000 W, 220 V. (i) What is the ratio of their resistances? (ii) In which of the above a thicker connecting wire or lead is required? Question. 35. A geyser has a label 2 kW, 240 V. What is the cost of running it for 30 minute, if the cost of electricity is Rs3.00 per unit? Question. 36. An electric kettle is rated 2.5 kW, 250 V. Find the cost of running the kettle for two hours at 60 paisa per unit. Current Electricity Question .1. Distinguish between terminal potential difference and e.m.f of a cell. Question .2. State the energy changes occurring in an electric cell. Question .3. State Ohm s law. Question .4. Calculate the equivalent resistance between A and B. Question .5. Write an expression for the resistance of a conducting wire in terms of its length and area of cross section. Question .6. Define the e.m.f E of a cell and the potential difference V across a resistor R in terms of work done in moving a unit charge. State the relation between these two works and the work done in moving a unit charge through a cell connected across the resistor. Take the internal resistance of the cell as r. Hence obtain an expression for the current I in the circuit. Question .7. Mention two factors on which the internal resistance of a cell depends. Question .8. Mention two factors on which the resistance of a wire depends. Question. 9. Differentiate between kilowatt and kilowatt-hour. Question. 10. Define current . Question. 11. What is the commercial unit of electrical energy? Express it in its SI value. Question.1 2. State and define the SI unit of current. Question. 13. Define the term 'electric potential'. Question. 14. What do you mean by potential difference between two points? Question. 15. State and define the SI unit of potential difference. Question. 16. What do you mean by conventional current? Question. 17. What do you mean by high potential and low potential? Question. 18. What do you mean by electrical resistance? State and explain the factors on which it depends. Question. 19. State and define the SI unit of resistance. Question. 20. State Ohm's law. What are its limitations? Question. 21. What is the mathematical form of Ohm's law? Question. 22. Differentiate between ohmic and non-ohmic conductors. State few examples of each. Question. 23. What do you mean by specific resistance (resistivity) of a material? What is its SI unit ? Question. 24. State two examples of each of the following: (i) material whose resistance increases with increase in temperature. (ii) material whose resistance decreases with increase in temperature. (iii) material whose resistance is not affected by change in temperature. Question. 25. Name the materials used for making connection wire. Give reason for your answer. Question. 26. Why and which materials are used for making standard resistors? Question. 27. What is an electric cell? What type of energy conversion takes place in it while in use? Question. 28. Define the terms e.m.f. and terminal voltage of an electric cell? State their unit. Question. 29. Differentiate between e.m.f. and terminal voltage of a cell. Question. 30. Define internal resistance of a cell. What is its unit? Question. 31. State and explain the factors on which internal resistance of a cell depends. Question. 32. Write a relation between e.m.f, terminal voltage and internal resistance of a cell. Question. 33. Differentiate between series and parallel combination of resistances. Question. 34. What do you mean by power-voltage rating of an appliance? Question. 35. Write a relation between watt, volt and ampere. Question. 36. A cell supplies a current of 0.6 A through a 2 ohm coil and a current of 0.3 A through a 8 ohm coil. Calculate the e.m.f and the internal resistance of the cell. Question. 37. Four cells each of e.m.f 2 V and internal resistance 0.1 ohm are connected in series. The combination is connected to an ammeter of negligible resistance, a 1.6 ohm resistor and an unknown resistor R1. The current in the circuit is 2 A. (i) Draw a labelled circuit diagram for the above arrangement. (ii) Calculate: (a) the total resistance of the circuit. (b) the total e.m.f. (c) the value of R1. (d) the potential difference across R1. Question. 38. Two resistors of 2 ohm and 3 ohm in parallel are connected to a cell of e.m.f 1.5 V and internal resistance 0.3 ohm. Draw a labelled circuit diagram showing the above arrangement and the current drawn from the cell. Question. 39. Four cells each of e.m.f 1.5 V and internal resistance 2.0 ohm are connected in parallel. The battery of cells is connected to an external resistance of 2.5 ohm. Calculate: (i) the total resistance of the circuit. (ii) the current flowing in the external circuit. (iii) the drop in potential across the terminals of the cells. Question. 40. Four resistance of 2.0 each are joined end to end to form a square ABCD. Calculate the equivalent resistance of the combination between any two adjacent corners. Question. 41. Find the equivalent resistance between the points A and O in the following circuit. O A Sound Question .1. The stem of a tuning fork is pressed against a table top. Answer the following questions: (i) Would the above action produce any audible sound. (ii) Does the above action cause the table to set into vibrations? (iii) If the answer above is yes, what type of vibrations are they? (iv) Under what conditions does the above action lead to resonance? Question .2. State any two characteristics of a wave motion. Question .3. If the amplitude of a wave is doubled, what will be the effect on its loudness? Question .4. Differentiate between forced vibrations and resonance. Question .5. How does the frequency and amplitudes affect a musical sound? Question .6. Under what condition does resonance occur? Question .7. Why is a loud sound heard at acoustic resonance? Question .8. The rear view mirror of motor bike starts vibrating violently at some particular speed of motor bike. (i) Why does this happen? (ii) What is the name of the phenomenon taking place? (iii) What could be done to stop the violent vibration? Question .9. Name the subjective property of sound related to its frequency and of light related to its wavelength. Question .10. Two friends were playing on identical guitars whose strings were adjusted to give notes of the same pitch. Will the quality of the two notes be the same? Give a reason for your answer. Question .11. Give one example each of natural vibration, forced vibration and resonance. Question .12. State three characteristics of a musical sound. Question .13. How does musical sound differ from noise? Question .14. How does a stretched string on being set into vibration, produce a audible sound? Question .15. Will the sound be audible if the string is set into vibration on the surface of the moon? Give reason for your answer. Question .16. A vibrating tuning fork is placed over the mouth of a burette filled with water. The tap is opened and the water level gradually falls. It is observed that the sound becomes the loudest for particular length of air column: (i) What is the name of the phenomenon taking place when this happens? (ii) Why does the sound become the loudest? (iii) What is the name of the phenomenon taking place when sound is produced for another length of air column and is not the loudest? (iv) How does the frequency of the loud sound compare with that of the tuning fork? (v) State the unit for measuring loudness. Question .17. What is Sonar? State the principle on which it is based. Question .18. State two ways by which the frequency of transverse vibrations of a stretched string can be decreased. Question .19. Explain why musical instruments like the guitar are provided with a hollow box. Question .20. What is the relation between frequency, wavelength and speed of a wave? Question. 21. A person standing between two vertical cliffs and 640 m away from the nearest cliff shouted. He heard the first echo after 4 seconds and the second echo 3 seconds later. Calculate: (i) the velocity of sound in air. (ii) the distance between the cliffs. Question. 22. A longitudinal wave of wavelength 1 cm travels in air with a speed of 330 m s-1. Calculate the frequency of the wave. Can this wave be heard by a normal human being? Question. 23. A certain sound has a frequency of 256 hertz and wavelength of 1.3 m. Calculate the speed with which this sound travels. What difference would be felt by a listener between this sound and another sound travelling at the same speed but of wavelength 2.6 m? Question. 24. A sound wave of wavelength 0.332 m has a time period of 10-3 s. If the time period is decreased to 10 4 s, calculate the wavelength and frequency of the new wave. Question. 25. Radio waves of speed 3 108 m s-1 are reflected off the moon and received back on the earth, the time elapsed between the sending of the signal and receiving it back on the earth s surface is 2.5 seconds. What is the distance of the moon from the earth? Question. 26. An observer stands at a distance of 850 m from the cliff and fires a gun. After what time gap will he hear the echo, if sound travels at a speed of 350 m s-1 in air? Question. 27. A pendulum has a frequency of 5 vibrations per second. An observer starts the pendulum and fires a gun simultaneously. He hears the echo from the cliff after 8 vibrations of the pendulum. If the velocity of sound in air is 340 m s-1, what is the distance between the cliff and the observer? Question. 28. The wavelength of waves produced on the surface of water is 20 cm. If the wave velocity is 24 m s-1, calculate: (i) the number of waves produced in one second. (ii) the time required to produce one wave. Question. 29. A radar is able to detect the reflected waves from an enemy aeroplane, after a time interval of 0.20 milliseconds. If the velocity of the waves is 3 108 m s-1, calculate the distance of the plane from the radar. Question. 30. A man standing in front of a vertical cliff fires a gun. He hears the echo after 3 seconds. On moving closer to the cliff by 82.5 m, he fires again. This time, he hears the echo after 2.5 seconds. Calculate: (i) the distance of the cliff from the initial position of the man. (ii) the velocity of sound. Question. 31. A radar sends a signal to an aeroplane at a distance 45 km away with a speed of 3 108 m s-1. After how long is the signal received back from the aeroplane? Spectrum and Colours Question .1. Write down the following and fill in the blanks spaces with appropriate colours: (a) Green + Magenta = ___________. (b) Red + _________ = Yellow. (c) Red + Blue = _____________. (d) Blue + _________ = Cyan. (e) Yellow + Blue = _________. (f) Magenta + ___________ = White. (g) _______ + Red = White. (h) Red + ________ + Green = White. (i) A red rose appears ________ when seen in green light. (j) A piece of red cloth appears red in white light because it _________ blue and green and ______ only red. Question .2. Write down the colour spectrum produced when white light is passed through a prism. Which of these colours is deviated most? Question .3. What is the wavelength of the electromagnetic wave whose frequency is 1012 Hz? Name this electromagnetic wave. Question .4. Show the effect of mixing two primary colours through labelled colour triangle. Question .5. Give one useful and one harmful effect of ultra violet radiation on the human body. Question .6. Define a pair of complementary colours. Name the colours in one such pair. Question .7. Define dispersion of light. Question .8. Explain briefly how white light gets dispersed by a prism. Question .9. Draw a diagram to show that white light can be split up into different colours. Draw another diagram to show how the colours can be combined to give the effect of white light . Question .10. Name the extreme colours in a pure spectrum of light. Question .11. State the equation for the relation between frequency and wavelength of light in vacuum. Question .12. Name any four regions of electromagnetic spectrum (other than visible light) in increasing order of wavelength. Question .13. Name any two electromagnetic waves which have a frequency higher than that of violet light. State one use of each. Question .14. Give one use each of the electromagnetic radiation given below: (i) microwave. (ii) Ultra violet radiation. (iii) Infrared radiation. Question .15. How would you show the presence of UV and IR rays in the spectrum? Question .16. When yellow paint and blue paint are mixed we get green colour. When yellow light and blue light are mixed, white light is obtained. Give reasons. Question .17. A green shirt is observed in blue light. What colour it will appear to be and why? Question .18. Explain why in day light an object appears red when seen through a red glass and black when seen through a blue glass? Question .19. Write the names of a pair of colours which combine to give white light. What is the name given to such a pair of colours ? Question .20. A flag is made up of three strips of cloth of yellow, white and cyan colours. Name the colour of a particular light in which this flag will appear to be of a single colour. Question .21. (i) White light is passed through a yellow filter. What colour is (colours are) seen on a screen plated at the end? (ii) If the light emerging from the yellow filter is then passed through a red filter, what will be seen on the screen placed at the end? Question .22. What will be the colour of an object which appears green in white light and black in red light ? Question .23. Give the approximate range of wavelengths in vacuum associated with UV rays and visible light. Question .24. A TV station transmits waves of frequency 200 MHz Calculate the wavelength of the waves if their speed in air is 3.0 108 m s-1. Question .25. Why are infrared radiations preferred over ordinary visible light for taking photograph in fog? Question .26. (i) What will be the colour of a blue flower when it is seen in magenta coloured light? (ii) Name another secondary colour of light in which the flower will show the same colour as it shows in the magenta coloured light. Question .27. (i) A particular type of high energy invisible electromagnetic rays help us to study the structure of crystals. Name these rays and give another important use of these rays. (ii) How does the speed of light in glass change on increasing the wavelength of light? Question .28. A room has window panes made of a special glass which can reflect green light, transmit red light, scatter blue light and absorb all the other colours of light. The room is illuminated with white light from inside. What colour will the window pane appear when seen from (i) inside the room (ii) outside the room? Refraction through Lenses Question .1. An object is placed in front of a lens between its optical centre and the focus. The image formed is virtual, erect and diminished. (i) Name the lens which forms this image. (ii) Draw a ray diagram to show the formation of an image with the above characteristics. Question .2. An object AB is placed on the principal axis of a convex lens as shown in figure below. Copy the diagram. Using three rays starting from B and the properties of the points marked F1, O and F2 obtain the image formed by the lens. c. Question .3. Figure below shows an object AB placed on the principal axis of a convex lens placed in air. F1 and F2 are the two foci of the lens. Copy the diagram: (i) Draw a ray of light starting from B and passing through O. Show the same ray after refraction by the lens. (ii) Draw another ray from B which passes through F2 after refraction by the lens. (iii) Locate the final image formed. (iv) Is the image formed real and inverted? Question .4. Is it possible to burn a piece of paper using a convex lens in day light without using matches or any direct flame? Draw a ray diagram to illustrate your answer. Question .5. Figure below shows an object AB placed on the principal axis of a lens L. The two foci of the lens are F1 and F2. The image formed by the lens is erect, virtual and diminished. Copy the diagram and answer the following questions: (i) Draw the outline of lens L used. (ii) Draw a ray from B, and passing through O. Show the ray after refraction by the lens. (iii) Draw a ray of light starting from B, which after passing parallel to the principal axis, is incident on the lens and emerges after refraction from it. (iv) Locate the final image formed. Question .6. Write the name of the (i) most sensitive and (ii) most insensitive part of the retina. Question .7. Draw a ray diagram to illustrate the action of a convergent lens as reading glasses or magnifying glass. Question .8. In an optical camera, state: (i) the nature of lens used. (ii) What is meant by f-number. (iii) Two characteristics of the image formed by the lens. Question .9. An erect, diminished and virtual image is formed when an object is placed between the optical centre and the principal focus of a lens. (i) Name the type of lens, which forms the above image. (ii) Draw a ray diagram to show the formation of the image with the above characteristics. Question .10. State two similarities between the photographic camera and the human eye. Question .11. Name any two essential parts of a single lens photographic camera. Question .12. A ray of light after refraction through a concave lens emerges parallel to the principal axis. Draw a ray diagram to show the incident ray and its corresponding emergent ray. Question .13. State the characteristics of the image of an extended source, formed by a concave lens. Question .14. The diagram given below shows an object O and its image I. Copy the diagram and draw suitable rays to locate the lens and its focus. Name the type of lens in this case. Question .15. An object is placed in front of a convex lens such that the image formed has the same size as that of the object. Draw a ray diagram to illustrate this. Question .16. Mention one similarity and one difference between the lens of a photographic camera and that of the human eye. Question .17. Draw outline ray diagram to show the formation of images through an eye in the following cases: (i) from a distance object for a short-sighted person and (ii) from the normal point of distinct vision for a long sighted person. Refraction at Plane Surfaces Question .1. State Snell s law of refraction. Question .2. The refractive index of air with respect to glass is defined as g a = sin i / sin r. (i) Write down a similar expression for a g in terms of angle i and angle r. (ii) In (i) above, if angle r = 90 what is the corresponding angle i called ? (iii) What is the physical significance of i in part (ii) above ? Question .3. What is meant by (i) Critical angle. (ii) Total internal reflection. Question .4. Draw a ray diagram to illustrate how a ray of light incident obliquely on one face of a rectangular glass slab of uniform thickness emerges parallel to its original direction. Mention which pairs of angles are equal. Question .5. Water in a pond appears to be only three quarter of its actual depth. (i) What property of light is responsible for this observation ? (ii) Illustrate your answer with the help of a ray diagram. Question .6. (i) With the help of a well labelled diagram show that the apparent depth of an object, such as a coin, in water is less than its real depth. (ii) How is the refractive index of water related to the real depth and the apparent depth of a column of water ? Question .7. Draw a ray diagram to illustrate the bending of a stick in water. Question .8. What is an optical fibre ? Give one practical use of an optical fibre. Question .9. Explain briefly what causes the twinkling of stars at night. Question .10. What is meant by the statement, the critical angle for diamond is 24 ? How is the critical angle of the material related to its refractive index ? Question .11. A glass slab is placed over a page on which the word VIBGYOR is printed with each letter in its corresponding colour. (i) Will the image of all the letters be in the same place ? (ii) If not, state which letter will be raised to the maximum. Give a reason for your answer. Question .12. What is meant by refraction ? Question .13. Express the refractive index of a medium. (i) In terms of the velocity of light; (ii) in terms of the angle of incidence i in air and the angle of refraction r in a denser medium. Question .14. If a ray of light passes from medium I to medium II without any change of direction, what can be said about the refractive indices of these media (angle i is not 0) ? Question .15. Mention two properties of a wave: one property which varies and the other which remains constant when the wave passes from one medium to another. Question .16. A prism deviates a monochromatic ray of light through an angle when the angle of incidence on the surface of the prism is i : (i) Draw a diagram showing the variation of with i . On your graph show the angle of minimum deviation. (ii) What is the relation between the angle of incidence and the angle of emergence when the ray suffers minimum deviation ? Question .17.Mention one difference between reflection of light from a plane mirror and total internal reflection of light from a prism. Question18. The velocity of light in diamond is 121,000 km s-1. What is its refractive index ? (Velocity of light in vacuum/air = 3 105 m s-1). Question19. Calculate the velocity of light in a glass block of refractive index1.5. (Velocity of light in air = 3 108 m s-1). Question20. If the refractive indices for a ray passing from air to water and from water to air, are denoted by symbols a w and w a respectively, write down the relation between a w and w a. If w a = 0.75, what will be the magnitude of a w. Question21.A glass-slab 2.5 cm thick is placed over a coin. If the refractive index of glass is 3/2, find the height through which coin is raised. Question22. If the speed of light in vacuum is 3 108 m s-1 and refractive index of water is 4/3, calculate the speed of light in water ? Force, Work, Energy and Power Question .1. State Newton s Second Law of motion both in words and in Equation form. Under what condition does this equation becomes F = ma ? Question .2. What is S I unit of force and how is it related to the CGS unit of force ? Question .3. Differentiate between mass and weight. Question .4. Write the S I unit of mass and weight. Question .5. A force is applied on (i) a rigid body and (ii) non rigid body. How does the effect of force differ in the two cases ? Question .6. Define (i) Work (ii) Power and (iii) Energy. Question .7. Write the expression for the work done by constant force acting on a body, which gets displaced from its initial position in a direction different from the direction of force. Or, How can the work done be measured when force is applied at an angle to the direction of displacement ? Question .8. When a body moves in a circular path how much work is done? Or, State the amount of work done by an object when it moves in a circular path for one complete rotation. Give reason to justify your answer. Question .9. How is work done related to the applied force ? Question .10. What should the angle between force and displacement be to get the (i) minimum work. (ii) Maximum work ? Question .11. Give an example when work done by force acting on a body is zero even though the body gets displaced from its initial position by the application of the force. Question .12. A truck driver starts off with his loaded truck. What are the major energy changes that take place in setting the truck in motion ? Question .13. State the energy change in an oscillating pendulum. Question.14. what is the main energy transformation that occurs in : (i) Photosynthesis in green leaves. (ii) Charging of battery. Question .15. Which physical quantity does the electron volt measure ? How is it related to the SI unit of this quantity ? Question .16. By what factor does the kinetic energy of a moving body change when its speed is reduced to half ? Question .17. Show that for the free fall of a body, the sum of the mechanical energy at any point in its path is constant. Question .18. Define the terms (i) mechanical advantage (ii) velocity ratio (iii) efficiency of a machine. Write an expression to show the relationship between mechanical advantage, velocity ratio and efficiency for a simple machine. Question .19. What is the relationship between the mechanical advantage and velocity ratio of (i) An ideal machine and (ii) Practical machine ? Question .20. How do you distinguish between a levers of the first order from a second or a third order lever ? Question .21. The following are the examples of levers. State the class of lever to which each one belongs giving the relative position of load (L), Effort (E) and Fulcrum (F). (i) Scissors. (ii) Sugar tongs. (iii) Nut cracker and (iv) Pliers. Question .22. Fig below shows a weight less lever in equilibrium. Neglect friction at the fulcrum F. (i) State the principle of moments as applied to the above lever. (ii) Define mechanical advantage and calculate its value for the given lever. (iii) Name the type(s) of lever which has M.A.>1. Question .23. Which class of levers has a mechanical advantage always greater than one ? What change can be brought about in this lever to increase its mechanical advantage ? Question .24. Which class of levers has a mechanical advantage always less than one ? Explain briefly with a diagram why their mechanical advantage is less than one. Question .25. Why is the mechanical advantage of a lever of the third class always less than one ? Give one example of this class of lever. Question .26. To use a machine as a force multiplier, which class of lever should preferred ? Draw a sketch of such a lever. Or, Draw a labelled sketch of a class II lever. Give one example of such a lever. Question .27. A pair of scissors and a pair of pliers belong to the same class of lever. (i) Which one has mechanical advantage less than one ? (ii) State the usefulness of such a machine whose mechanical advantage is less than one. Question .28. Explain why scissors for cutting cloth may have blades much longer than the handles; but shears for cutting metals have short blades and long handles. Question .29. Give two reasons why the efficiency of a single movable pulley system is not 100%. Question .30. A combination of a movable pulley P1with a fixed pulley P2 is used for lifting up a load W. (i) State the function of the fixed pulley P2. (ii) If the free end of the string moves through a distance x, find the distance by which the load W is raised. Question .31. Name a type of single pulley that can act as a force multiplier. Draw a labelled diagram of the above named pulley. Question .32. A block and tackle pulley system has a velocity ratio 3. (i) Draw a labelled diagram of this system. In your diagram, indicate clearly the points of application and the directions of the load and effort. (ii) Why should the lower block of this pulley system be of negligible weight ? Question.33. Define an inclined plane. Question34. A body of mass 1 kg is thrown vertically up with an initial speed of 15 ms-1. What is the magnitude and direction of the force due to gravity acting on the body when it is at the highest point ? Question35. The weight of two bodies is 2.0 N and 2.0 kgf respectively. What is the mass of each body ? Question36. Two balls of mass ratio 1 : 2 are dropped from the same height. (i) State the ratio between their velocities when they strike the ground and (ii) the ratio of the forces acting on them during motion. Question37. A force of 100 N acts on a body for 5 seconds and produces a velocity of 50 ms-1. Find the mass of the body. Question38. A cricket ball of mass 70 g, moving with a velocity of 0.5 m s-1 is stopped by a player in 0.5 s. What is the force applied by the player to stop the ball ? Question39. A man of mass 60 kg runs up a flight of 30 steps in 15 second. If each step is 20 cm high, calculate the power developed by the man. Take g =m 10 ms-2. Question38. How fast should a man weighing 60 kg run so that his kinetic energy is 750 J. Question39. A block of mass 30 kg is pulled up a slope with a constant speed by applying a force of 200 N parallel to the slope. A and B are initial and final positions of the block. (i) Calculate the work done by the force in moving the block from A to B. (ii) Calculate the potential energy gained by the block. Question40. A body of mass 1 kg falls from a height of 5 m. How much energy does it possess at any instant. Take g = 9.8 ms-2. Question41. A bullet of mass 50 g is moving with a velocity of 500 ms-1. It penetrates 10 cm into a still target and comes to rest. (i) Calculate the KE possessed by the bullet. (ii) The average retarding force offered by the target. Question42. An engine can pump 30000 litre of water to a vertical height of 45 m in 10 minutes (g = 9.8 ms-1). Calculate the work done by the machine and its power (density of water 1000kgm-3 and 1000 litre = 1 m3). Question43. A machine raises a load of 750 N through a height of 16 m in 5 second. Calculate the power at which the machine works. Question44. If power of a motor is 40 kW, at what speed can it raise a load of 20,000 N ? Question45. A ball of mass 0.20 kg is thrown vertically upwards with an initial velocity of 20 ms-1. Calculate the maximum potential energy it gains as it goes up. Question46. The work done by the heart is 1 joule per beat. Calculate the power of the heart if it beats 72 times in one minute. Question47. Two bodies, A and B of equal mass are kept at heights 20m and 30 m respectively. Calculate the ratio of their potential energies. Question48. The diagram below shows the use of a lever. (a) State the principle of moments as applied to the above lever. (b) Give an example of this lever. (c) If FA = 10 cm, AB = 500 cm, calculate the minimum effort required to lift the load. Question49. The crow bar is a type of lever as shown below. A crowbar of length 150 cm has its fulcrum at a distance of 25 cm from the load. Calculate the mechanical advantage of this crowbar. Question50. A cook uses a fire tong of length 28 cm to lift a piece of burning coal of mass 250 g. If he applies his effort at a distance 7 cm from the fulcrum, what is the effort in SI unit ? Take g = 10 ms-2. Question51. A woman draws water from a well using a fixed pulley. The mass of the bucket and water together is 6.0 kg. The force applied by the woman is 70 N. Calculate the mechanical advantage. (Take g = 10 ms2). Question52. Combination of a movable pulley P1with a fixed pulley P2used for lifting up a load 20 kgf. Calculate the effort applied at the free end of the string, neglecting the weight of the pulley P1 and friction. Question53. In the arrangement of four pulleys, a load is attached to the movable lower block and an effort is applied at the free end of the string. Calculate the mechanical advantage of the system. Question54. A block and tackle pulleys of 5 pulleys consists of 3 pulleys in the upper block and 2 pulleys in the lower block . If the load is raised by 1 m, through what distance will effort move ? Question55. A uniform metre scale is kept in equilibrium when supported at the 60 cm mark and a mass M is suspended from the 10 cm mark. State with reason whether the weight of the scale is greater than, less than or equal to the weight of mass M. *************************
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